Initial application of novel compound-specific 34S analysis to the Cariaco Basin

硫是许多生物地球化学过程的重要组成部分，包括大气化学和气溶胶形成、微生物生态学、海洋缺氧和大规模灭绝、有机物保存、石油生成和酸化，以及古代地球海洋和大气的氧化作用。硫的稳定同位素组成（即它们的dS值）可以为这些研究提供相当大的见解，因为硫的许多氧化还原转化会引起大量的诊断性同位素分馏。这些分馏物可以保存在含硫产品中，作为过去工艺的指纹。在这方面，有机硫（OS）是s同位素信息最丰富但利用最少的储集层之一。直到最近，还没有有效的方法来获取单个OS化合物记录的同位素信息。pi最近开发了一种新的GC/ICPMS分析方法（Amrani et al., 2009），现在我们可以测量仅含有皮摩尔s的单个OS化合物中的d34S。他们建议研究沉积成岩过程中有机化合物的渐进硫化作用。关于脂质硫化的三个具体问题将得到解决：i)单个化合物的d34S值是否记录了硫掺入的同化与异化途径？ii)分子d34S值是否因分馏而与其无机S源相偏移？iii)不同化合物是否记录了不同深度的硫化物和/或硫酸盐d34S值？该提案将有助于支持一个重要的新分析工具的开发和部署，即化合物特异性d34S分析。他们的研究结果和该方法的更广泛的潜力可能会影响我们对全球碳循环的理解，以及它对气候变化的所有深远影响，因为人们对硫化的途径仍然知之甚少，对沉积物中有机物的埋藏和保存施加了一级控制。该提案还将支持加州理工学院的一名博士生的教育，该博士生（完成后）可能会成为化合物特定S同位素分析的世界专家，并将这项技术带到其他实验室。

Sulfur is an important component of many biogeochemical processes, spanning atmospheric chemistry and aerosol formation, microbial ecology, ocean anoxia and mass extinctions, organic matter preservation, petroleum generation and souring, and the oxygenation of the ancient Earth's oceans and atmosphere. The stable isotopic compositions of sulfur species (i.e., their dS values) can provide considerable insight in these pursuits, because many redox transformations of sulfur induce large and diagnostic isotopic fractionations. These fractionations can be preserved in sulfur-bearing products, where they serve as fingerprints of past processes. In this regard, organic sulfur (OS) is among the richest "but least utilized" reservoirs of S-isotopic information. Until recently there has been no effective way to access the isotopic information recorded by individual OS compounds. The PIs have recently developed a novel GC/ICPMS analytical approach (Amrani et al., 2009) that now allows us to measure d34S in individual OS compounds containing just picomoles of S. They propose to study the progressive sulfurization of organic compounds during sedimentary diagenesis. Three specific questions will be addressed regarding the sulfurization of lipids: i) Do d34S values of individual compounds record assimilatory versus dissimilatory pathways of sulfur incorporation? ii) Are molecular d34S values offset from their inorganic S sources as a result of fractionations? iii) Do different compounds record sulfide and/or sulfate d34S values from different depths? This proposal will help support the development and deployment of an important new analytical tool, namely compound-specific d34S analysis. The results of their research and the broader potential of the method are likely to impact our understanding of the global carbon cycle, and all of its far-reaching impacts on climate change, because the still poorly understood pathways of sulfurization exert a first-order control on the burial and preservation of organic matter in sediments. The proposal will also support the education of a PhD student at Caltech, who (upon completion) will presumably be the world's expert in compound-specific S isotope analyses and will carry this technique to other labs.